A wide variety of disposable absorbent articles are designed not only to be efficient in the absorption of body fluids such as urine, blood, menses and the like, but also to be sanitary and comfortable in-use, are known in literature. Disposable absorbent products of this type generally comprise a fluid-permeable topsheet material, an absorbent core (or a fluid storage layer), and a fluid-impermeable backsheet material. Various shapes, sizes and thicknesses of such articles have been explored in an attempt to make their use more comfortable and convenient.
For some time now, studies for such disposable absorbent articles have been primarily focused on the absorptive capacity of the article. As a result, various absorbent polymers with high absorptive power have been developed. Such known superabsorbent materials (also known as hydrogel-forming absorbent polymers) are capable of absorbing from about 30 to 60 grams of water per gram of polymer.
More recently, research has been focused on the removal of foul odors and the prevention of skin diseases such as dermatitis, rash and redness caused by wearing a disposable absorbent article for a relatively long time. Many body fluids have an unpleasant odor (or an malodor), or develop such an odor when in contact with air and/or bacteria for prolonged periods. Additionally, urine and/or other exudates absorbed into the absorbent article are converted to ammonia by urease produced by skin-flora, i.e., a group of normal microorganisms on the skin. This ammonia, in turn, may cause dermatitis, rash and/or other forms of skin irritation. Such disease of the skin in infants can be a serious medical matter which, in extreme cases, can result in death.
Antimicrobial materials and bactericides in general are chemical compositions that are used to prevent microbiological contamination and deterioration of products, materials, and systems. Such antimicrobial materials and bactericides can also effectively work for the removal or reduction of foul odors developed from disposable absorbent articles which has already absorbed body fluids. However, depending on the manner of the application of antimicrobial materials or bactericides in disposable absorbent articles, it is found that such antimicrobial materials and bactericides tend to affect the absorptive capacity of disposable absorbent articles.
For example, Japanese Patent (Kokoku) Publication No. H4-17058 discloses a disposable diaper which includes an absorbent layer containing a superabsorbent material and a antimicrobial material included in the superabsorbent material. Similarly, Japanese Patent (Kokai) Publication No. 145-277143 discloses a disposable diaper which includes a superabsorbent material containing an odor reduction material. Metalphthalocyanine derivatives are disclosed in H5-277143 as examples of the odor reduction material. Further, Japanese Patent (Kokai) Publication No. S64-25856 discloses a sanitary napkin which includes an absorbent sheet including a superabsorbent material and a metalphthalocyanine derivative as an odor reduction material. In those structures disclosed, the antimicrobial or odor reduction material is in contact with the superabsorbent material, as a result, the absorptive capacity of the superabsorbent material tends to be decreased because of the existence of the antimicrobial or odor reduction material.
To prevent the antimicrobial materials and/or bactericides from affecting the absorptive capacity of disposable absorbent articles, it is preferred that the antimicrobial materials and/or bactericides is provided in a layer which is isolated from the superabsorbent material. However, the antimicrobial materials and/or bactericides tend to be expensive and increase the manufacturing cost of the disposable absorbent articles, therefore, an appropriate (and a minimum) amount of the antimicrobial materials and/or bactericides needs to be used while providing an effective odor and/or antimicrobial reduction function. Further, it is not generally easy in the manufacturing process to control the total amount of the antimicrobial materials and/or bactericides which is applied to a component material(s) of disposable absorbent articles.
Based on the foregoing, there is a need for disposable absorbent articles which have an effective odor and/or antimicrobial reduction function with a minimum manufacturing cost increase. Further, there is also a need for disposable absorbent articles which have a structure that can easily control the total amount of odor and/or antimicrobial reduction material applied thereto.